Polarization switching antenna system



July 24, 1956 s. HERSHFIELD 2,756,422

POLARIZATION SWITCHING ANTENNA SYSTEM 3 Sheets-Sheet 1 Filed Jan. 2, 1952 1N VENTOR ATTORNEY $4791 6. @17. jg J6. 312 919 y 24, 1956 s. HERSHFIELD POLARIZATION SWITCHING ANTENNA SYSTEM 3 Sheets-Sheet 2 Filed Jan. 2, 1952 T T 4 WM m H m w M 5 BY mz ig y ATTORNEY July 24, 1956 s. HERSHFIELD 2,756,422

POLARIZATION SWITCHING ANTENNA SYSTEM Filed Jan. 2. 1952 3 Sheets-Sheet 3 ATTORNEY I NV E NTOR United States Patent POLARIZATION swrrcme ANTENNA SYSTEM Sanford Hershfield, Middle River, Md., assignor to The Glenn L. Martin Company, Middle River, Md., a corporation of Maryland Application January 2, 1952, Serial No. 264,455

'13 Claims. (Cl. 343786) This invention pertains to an antenna system adapted to selectively radiate or receive electro-magnetic energy having any one of several polarizations.

Depending upon such factors as atmospheric conditions, location of the apparatus, etc., it is frequently desirable to provide a means for selectively receiving or transmitting radio energy in any of the several polarizations. This is especially true where search radar equipment is involved since, under certain conditions, one type of polarization may give superior results while under other conditions a different type may be preferable.

It is an object of this invention to provide an antenna system which may be connected to a source of a given polarization and which is capable of selectively transmitting the energy in any of several different polarizations.

It is a further object to provide a polarization switching element which may be inserted in and form part of a conventional wave guide transmission line and which will convert radio energy of a given polarization to any desired other polarization.

Another object is to provide a horn antenna which may be used in conjunction with such a polarization switch and which will radiate the energy obtained from the output of the polarization switch regardless of its polarization while maintaining substantially constant field patterns in both the vertical and horizontal planes.

Further objects will appear from the following description and claims taken in view of the appended drawing.

In the drawing:

Fig. 1 is a perspective view of one form of the antenna system of this invention.

Fig. 2 is a top plan view of the polarization switch and shows, diagrammatically, a suitable control system therefor.

Fig. 3 is a transverse sectional view of the polarization switch taken on the line 33 of Fig. 4.

Fig. 4 is a longitudinal sectional view of the polarization switch taken on the line 4-4 of Fig. 3.

Fig. 5 is a perspective view of a modified form of antenna system.

Figs. 6 through 20 are diagrammatic figures showing the polarizations obtaining at various points along the antenna system of Fig. 1.

Fig. 1 shows the antenna system including the input wave guide section 2, feeding a polarization switching unit 3, the output of which is supplied through a section of square wave guide 4 to the input of a horn antenna 5. Interposed between the section 2 and the switch 3 is a short transition section 6, while a similar transition section 7 is interposed between the polarization switch 3 and the wave guide 4, these transition sections 6 and 7 serving to blend the walls of the various sections together without any abrupt discontinuity which might produce standing waves within the guide. As shown in Fig. 1, the polarization switching unit 3 is rotated about the axis of the guide through an angle of 45 relative to theother sections. 7

2,756,422 Patented July 24, 1956 Turning now to Figures 2 and 4, it is seen that the polarization switching unit 3 consists of a lower wave guide portion 9 having front and rear side walls 10 and 11, a fixed bottom wall 12 and a movable top wall member 13. As best shown in Fig. 3, the wall member 13 is in the form of a hollow box-like member having the lower portion 14 of its side walls 15 spaced from the walls 10 and 11 and then ofiset inwardly as at 16 and then upwardly as at 17 to merge into the top plate 18 so as to form therewith resonant choke chambers 19 communicating with the interior of the wave guide. The effect of this construction is the same as if the lower wall of member 13 were directly electrically shorted to the adjacent side walls 10 and 11 but eliminates the inherent difiiculties that would obtain were it attempted to literally short the movable member 13 to the walls 10 and 11 by suitable sliding electrical contacting members. Supporting the wall member 13 is a pair of links 20 and 21 pivoted at 22 to the member 13 and pivoted at 23 to arms 24 of bell cranks 25, in turn pivotally carried as by bolts 26 adjacent the upper portion of the side walls of the unit. Each bell crank includes an upwardly extending actuating arm 27 to which the opposite ends of a link 28 are pivoted as at 29. Obviously, by shifting link 28 toward one end or the other, the wall 13 may be raised or lowered relative to the bottom wall so as to vary the efiective height of the wave guide portion 9.

To actuate link 28, a pair of solenoids 30 and 31, rigidly carried by the side wall of the unit, are employed. The plungers 32 and 33 of the solenoids extend toward one another and are connected, as will be later described, to a rod 34 which extends through an opening 35 formed in an angle member 36 rigidly carried by the link 28. A nut 37 carried on the end of rod 34 cooperates with a shoulder 38 thereon for preventing relative axial movement of the rod and angle member. As indicated in Fig.

2, the opening 35 is larger than the diameter of the rod 34 to permit limited movement of the angle member 36 relative to the rod to compensate for the fact that link 28 has a slight vertical movement as well as an endwise movement. Energization of either of the solenoids will pull rod 34 and link 28 in the direction toward that particular solenoid and will move wall member 13 up or down a corresponding amount.

Each of the plungers 32 and 33 has its inner end portion 39 reduced in diameter and threaded. Portion 39 of plunger 33 is screwed directly into a mating opening in the right hand end of rod 34 while portion 39 of plunger 32 is threaded into an elongated sleeve nut 40 which, in turn, is threaded upon a reduced tip portion 41 of the rod 34.

To return the wall 13 to its neutral position upon deenergization of the solenoids, a centering spring unit 42 is provided. As indicated in Fig. 2, centering unit 42 comprises a pair of collars 43 and 43 slidable upon the central portion of rod 34 and urged outwardly by a spring 44. Collar 43 normally abuts against the inner end of sleeve nut 40 while collar 43 abuts against a shoulder 45 formed on the rod 34. The spring unit further includes a sleeve-like housing 46 rigidly carried by the side wall of the switching unit. Lips 47 and 48 at the ends of the housing are adapted to engage the ends of collars 43 and 43' adjacent their periphery. The arrangement is such that if rod 34 is shifted in either direction from its normal or neutral position shown, the spring 44 will tend to restore it to neutral. For example, if rod 34 is shifted to the left by energization of solenoid 30, collar 43' will be moved by shoulder 45 so as to compress spring 44, collar 43 being held against movement by lip 48. Thus, when the solenoid 30 is deenergized, the spring 44 will return the rod to its neutral position.

Any desired means'could be used for selectively energizing solenoids 30 and 31. For example, a suitable arrangement is diagrammatically indicated in Fig. 2 wherein solenoids 30 and 31 are shown as being connected by suitable leads 49 and 50 to terminals 51 and 52 of a three position selector switch 53. The movable contact arm 54 of the switch is connected to a suitable power supply shown as a battery 55. The arrangement is such that when the switch is moved to the terminal 51, solenoid 30 will be energized to shift the wall 13 downwardly, while if the switch is moved to terminal 52, solenoid 31 will shift the wall upwardly. When the switch is in its central position 57, neither solenoid will be energized and the wall member 13 will be in its neutral position.

Suitable adjustable stops, such as eccentrics 56, are provided to engage discs 56' on the ends of the solenoid plungers to stop the movement of the wall at the desired positions. For example, stops 56 may be adjusted so as to provide for vertical polarization when solenoid 30 is energized and for horizontal polarization when solenoid 31 is energized, while when neither is energized, spring 44 will hold the parts in position to produce circular polarization.

As will be later described in detail, the polarization switching effect is due to the fact that in a rectangular wave guide, the energy polarized parallel to one of the pairs of walls will have a different velocity along the guide than that polarized parallel to the other pair of walls. By changing the relative shape of the wave guide section 9, the relative phase velocities of two rectangularly related components travelling along the guide can be altered so that at the output one of the components will have been shifted in phase relative to the other. Sufiice it to say at the present time that if the wall 13 is moved to a position wherein the guide portion of the switching unit is substantially square (solenoid 30 fully energized), there will be no relative phase shift, while if the wall member 13 is moved to its other limiting position (solenoid 31 fully energized), one component of the energy will undergo a relative phase shift of 180 with respect to the other. In the neutral position, approximately half-way between these extremes (neither solenoid energized), a relative phase shift of 90 will obtain. As will later be explained, these will produce at theoutput of the polarization switching unit, vertical, horizontal, and circular polarizations, respectively.

Considering now the antenna 5, best shown in Fig. 1, it is well known that the radiation pattern from a horn antenna will be dependent upon both the physical dimensions ofthe opening and the polarization of the energy. By proper selection of the size and shape of the opening, it is usually possible todesign a horn which will maintain its azimuth and elevation beamwidths reasonably close to the desired values regardless of the polarization employed. Unfortunately, however, since it is normally desired that the beamwidth in azimuth be different from that in elevation, the required antenna opening will not ordinarily be square, but rather will be rectangular. Therefore, if the horn has any finite length, circularly or elliptically polarized waves could not be transmitted therethrough without a phase shift which would adversely affect the polarization.

In the instant case, to obtain the desired beamwidths in azimuth and in elevation regardless of what polarization was involved, the open end of the horn was determined to be about .67k wide by 125k high, where A represents the wave length in space at the design frequency. Since the section 4 of the wave guide extending from the polarization switch 3 to the antenna is square in section to thereby avoid any undesirable change in the polarization of a circularly polarized wave travelling therethrough, it is necessary to flare out the walls of the horn as at 8 to match the desired shape of the antenna opening. Therefore a phase shift will obtain between the horizontal and vertical components of a circularly or to cause a relative phase shiftof m1- between the hori-' zontal and vertical components of a circularly or elliptically polarized wave travelling therealong, where n is any integer. As will be later explained, if n is even, the energizing wave will be polarized exactly the same as that travelling through wave guide 4. If n is odd, the energizing wave will be similarly polarized, but in the opposite sense.

By providing the relatively sharply flared section 8 followed by the constant section rectangular portion 8', the over-all length of the horn antenna 5 may be kept to a minimum since the relative phase shift is greater per unit length in the rectangular portion than in the flaring portion. However, other configurations could obviously be employed so long as the length is proportioned to the internal dimensions so as to give the desired mr phase shift between the horizontal and vertical components of a wave travelling therethrough.

The operation of the system will now be explained with the aid of 'Figs. 6 through 20. Figs. 6 through 10 show the polarizations obtaining at various points along the system when the switching unit is adjusted to provide vertical output from the antenna 5, Figs. 11 through 15 show the conditions prevailing at the corresponding points when the unit is set for circular polarization, and Figs. 16 to 20 show the corresponding conditions when the switching unit is set to provide horizontal polarization. Fig. 6 indicates the polarization of the wave as it travels along the input section 2. Fig. 7 shows the condition at the input end of switching unit 3 and Fig. 8 shows the condition at the output end of the switching unit. Figs. 9 and 10 show the polarization obtained at the input and output ends of the horn antenna.

As shown in Fig. 6, the energy being transmitted along wave guide 2 is polarized vertically as indicated at E. However, when this energy is fed into theswitching unit 3, due to the fact that the walls of unit 3 are oriented at 45 with respect to the walls of section 2, the energy will be divided into two components, a and b, parallel to the walls of the unit 3. The relative phase velocities of these components will, of course, depend upon the relative widths of the two pairs of walls. Since in Fig. 7 the wall 13 has been adjusted to a position wherein the wave guide portion is square in section, both components a and b will travel therealong with the same phase velocity and will be exactly in phase with one another at the output end as indicated in Fig. 8. T hey will therefore recombine to produce a single component B, still vertically polarized, which will be transmitted along section 4 and through horn 5 without change. Thus, as indicated in Fig. 10 with the wall 13 adjusted as shown in Fig. 7, vertical polarization will be produced at the output of the horn 5.

Turning now to Figs. 11 to 15, it is seen that wall 13 has been moved somewhat outwardly. The vertically polarized input energy will again be divided into its two components a and b at the input of the unit 3 but, in this case, due to the fact that the wave guide portion of the switching unit is no longer square, component b will travel therealong with a greater phase velocity than will component a. The wall 13 is assumed to have been moved to such a position that by the time these components have reached the output end of the unit 3, component b will lead component a by This corresponds to a true circular polarization of the energy. As these components a and b travel along the square wave guide section 4, they will both travel at the same velocity so that at the input of the antenna 5, they will still be 90 out of phase with one another. At this point, as shown in Fig. 14, each of the components a and b may be considered as constituted by two components a and a and b and b respectively, parallel to the corresponding walls of the antenna section. However, due to the fact that the top and bottom walls of the antenna section are flared outwardly at 8 and are spaced further apart than the side walls throughout the portion 8', the horizontal components a and b will travel therealong at a faster rate than the vertical components a b As previously indicated, the length of the horn 5 is chosen so that at the output end of the horn, horizontal components a and b will have advanced in phase some multiple of 180 relative to vertical components a and b In this example, it has been assumed that this phase shift is 180 Therefore, the conditions obtaining at the output of the antenna are as diagrammatically indicated in Fig. 15. Component a whill have advanced 180 relative to (1 while 12 will have similarly advanced 180 with respect to h. Components :1 and b are the equivalent of, and may be replaced by, components a and lagging 180 behind a and b and polarized in the opposite directions. It will be noted that a and a are now in phase and may be combined into a single component A. Similarly, components b and b may be combined into a single component B. Also it should be noted that components A and B are exactly 90 out of phase with one another. Once again, this corresponds to the condition for circular polarization. Note, however, that the sense of the circular polarization has been reversed from that obtaining at the output of the switching unit 3. At the output of polarization switch 3, the polarization vector would be rotating counter-clockwise as indicated in Fig. 15. By similar analysis it can be readily shown that if the antenna section 5 were of a length to cause a relative phase shift therein equal to an even multiple of 180, say 360, the sense of the polarization at the output would be the same as that at the output of the switching unit 3.

Figs. 16 to 20 show the conditions obtaining when the wall 13 has been moved still further outwardly to obtain horizontal polarization. Here again, the input energy is divided into its two components a and b at the input of the switching unit. Here however, since wall 13 has been moved further outwardly, component b will have a still greater phase velocity relative to that of component a. Wall 13 will have been shifted to a position such that at the output of the unit 3, component b will lead component a by a full 180 as indicated in Fig. 18. Here again, component b may be replaced by a component b in phase with component a and polarized oppositely to component 12. Components b and a may be combined into a single horizontal component C which will travel along through section 4 and horn 5 without change of polarization and the energy will be radiated polarized in the horizontal plane.

Obviously if the wall 13 is adjusted to any other position intermediate the Fig. 7 and Fig. 17 positions, elliptical polarization will result. In fact the circular polarization obtained in the Fig. 12 or neutral position as well as the horizontal and vertical plane polarizations are but specialized cases of elliptical polarization. However, it should be noted that the angle of the major axis of the polarization ellipse and the ratio of the major to the minor axis will be interdependent and will, of course, vary depending upon the position of the wall 13. Obviously where a particular elliptical polarization is desired, the appropriate stop 56 may readily be adjusted so as to restrict the movement of its solenoid plunger and hence position the wall 13 at the desired intermediate position.

Fig. 5 shows a modification wherein a second polarization switching unit 3 is interposed between transition section 7 and square section 4. This unit 3', like section 4 and antenna 5, has its walls oriented at 45 to the walls of unit 3. By providing means as suggested above for holding the movable walls of each of these units at any desired intermediate position, the entire gamut of polarizations can be obtained at the output of the antenna 5'. As indicated in Fig. 5, antenna 5' may be of any desired length since the otherwise troublesome phase shift that would obtain therein can readily be compensated for by proper adjustment of one or both of the switching units 3 or 3'. The operation of the Fig. 5 embodiment can readily be understood by following the same reasoning used in discussing Figs. 6 to 20.

It is thus seen that applicant has provided an antenna system whereby Waves of any selected polarization can be readily produced from a source of predetermined polarization and yet the arrangement can readily be designed to provide substantially constant field patterns in both the horizontal and vertical planes regardless of the type of polarization appearing at its output. While, for ease of illustration, the assembly has been shown as extending along a straight axis, the various wave guide sections can obviously be bent around corners or twisted in accordance with normal practice without adversely affecting the operation.

Since the amount of relative phase shift per unit length in a rectangular section will vary with the ratio of the width to the height, a switching unit in which the movable wall is movable to a considerably greater extent than that shown in Figs. 2 to 4 could be theoretically used thus permitting a correspondingly shorter unit. However, the greater the movement of the wall, the greater will be the discontinuity produced in the guide and as a result the over-all standing wave ratio could not be maintained at the desired low value. Therefore it is highly desirable that the switching unit be made relatively long so that a correspondingly small movement of the wall will produce the desired polarization shift from vertical to horizontal. With the switching unit shown, excellent results were produced with an over-all movement of the top wall (from the Fig. 7 to the Fig. 17 position) of substantially one-half inch, the unit being slightly under three inches in width and approximately 18 inches long, and the frequency employed being 2800 m. 0.

While throughout this description the assembly has been described as being used for transmitting energy, it is believed obvious that the same results would be prodnced were it used for receiving. By proper adjustment of wall 13, received energy of any selected polarization could be converted into energy of a given polarization travelling along the guide 2.

It is apparent that many changes could be made from the specific arrangement shown without in any way departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. A wave guide for electromagnetic waves comprising a first section of generally rectangular wave guide adapted to transmit radio waves therethrough polarized parallel to one pair of its walls, a second section of generally rectangular wave guide coupled to the output end of said first section and being oriented about the axis of said guide so that its walls lie in planes at angles to the walls of said first section, to resolve said waves into two substantially rectangularly related components polarized parallel to its walls, one wall of said second section being mounted for movement toward and away from its opposite wall to vary the relative phase velocity of said components travelling therethrough with concomitant varying of the relative phase of said components emerging at the end of said second section.

2. A wave guide for electromagnetic waves comprising a first section of generally rectangular wave guide adapted to transmit radio waves therethrough polarized parallel to one pair of its walls, a second section of generally rectangular wave guide coupled to the output end of said first section and being oriented about the axis of said guide so that its walls lie in planes at angles to the walls of said first section, to resolve said waves into two substantially rectangularly related components polarized parallel to its walls, one wall of said second section being mounted for movement toward and away from its opposite wall to vary the relative phase velocity of said components travelling therethrough with concomitant varying the relative phase of said components emerging at the end of said second section, said one wall being movable at least between two positions so related to the length of said second section as to produce a relative phase shift between such components travelling through said section varying from in one position to at least 180 in said second position.

3. A wave guide for electromagnetic waves compri.,- ing a first section of generally rectangular wave guide adapted to transmit radio waves therethrough polarized parallel to one pair of its walls, a second section or" generally rectangular wave guide coupled to the output end of said first section and being oriented about the axis of said guide so that its walls lie in planes at angles to the walls of said first section, to resolve said waves into two substantially rectangularly related components polarized parallel to its walls, one wall of said second section being mounted for movement toward and away 1 from its opposite wall to vary the relative phase velocity of said components travelling therethrough with concomitant varying the relative phase of said components emerging at the end of said second section, said one wall being movable at least between two positions so related to the length of said second section as to produce a relative phase shift between such components travelling through said section varying from 0 in one position to at least 180 in said second position, and a third section of generally rectangular wave guide having its walls oriented at angles relative to said second section whereby to recombine said components into a single wave polarized parallel to one pair of its walls when said movable wall is in said one position and polarized parallel to its other pair of walls when said movable wall is in said second position.

4. A wave guide for electromagnetic waves comprising a first section of generally rectangular wave guide adapted to transmit radio waves therethrough polarized parallel to one pair of its walls, a second section of generally rectangular wave guide coupled to the output end of said first section and being oriented about the axis of said guide so that its walls lie in planes at angles to the walls of said first secetion, to resolve said waves into two substantially rectangular-1y related components polarized parallel to its walls, one wall of said second section being mounted for mo ement toward and away from its opposite wall to vary the relative phase velocity of said components travelling therethrough with concomitant varying the relative phase of said components emerging at the end of said second section, said one wall being movable at least between two positions so related to the length of said second section as to produce a relative phase shift between such components travelling through said section varying from 0 in one position to at least 180 in said second position, and a third section of generally rectangular wave guide having its walls oriented at angles relative to said second section whereby to recombine said components into a single wave polarized parallel to one pair of its walls when said movable wall is in said one position and polarized parallel to its other pair of walls when said movable wall is in said second position, said third section of wave guide including an open-ended radiating portion having one pair of its walls wider than the other pair whereby the phase velocity through said portion of energy polarized parallel to said one pair of walls will differ from that of energy of the same frequency polarized parallel to said other pair of Walls, and said open-ended portion having a length proportioned to the widths of said walls and to the frequency of said energy such that in travelling the length of said portion said first mentioned energy will undergo a phase shift of n times relative to said second mentioned energy, where n is any integer. s

5. A wave guide for electromagnetic waves comprising a first section of generally rectangular wave guide adapted to transmit radio waves therethrough polarized parallel to one pair of its Walls, a second section of gen: erally rectangular wave guide coupled to the output end of said first section and being oriented about the axis of said guide so that its walls lie in planes at angles to the walls of said first section, to resolve said waves into two substantially rectangularly related components polarized parallel to its walls, one wall of said second section being mounted for movement toward and away from its opposite wall to vary the relative phase velocity of said components travelling therethrough with concomitant varying the relative phase of said components emerging at the end of said second section, said one wall being movable at least between two positions so related to the length of said second section as to produce a relative phase shift between such components travelling through said section varying from 0 in one position to at least 180 in said second position, and a third section of generally rectangular wave guide having its walls oriented at angles relative to said second section whereby to recombine said components into a single wave polarized parallel to one pair of its walls when said movable wall is in said one position and polarized parallel to its other pair of walls when said movable wall is in said second position, said third section also including a portion having one of its walls movable between two positions so related to its length as to produce a further phase shift between components polarized parallel to its two pair of walls varying from 0 in one'position to at least 180 in the other position.

6. A polarization switch for varying the polarization of electromagnetic energy transmitted therethrough comprising a generally rectangular wave guide section of predetermined length having one side wall thereof mounted for movement toward and away from the opposite side wall, means for coupling wave energy into said wave guide at one end thereof with electromagnetic energy polarized in a plane lying at 45 to the planes of the side walls of said section, said energy will be resolved into two equal substantially rectangularly related components parallel to the corresponding walls of said guide, means for moving said one wall to vary the phase velocity of said components along said guide with concomitant varying the relative phase of said components emerging at the ,end of said second section, said wall being movable between first and second positions so related to the length of said section that in said first position said components will be in phase at said output end and in said second position said components will be 180 out of phase at said output end and at intermediate positions said components will be between zero and 180 out of phase whereby the resultant electromagnetic energy at the output of said section will be elliptically polarized when said wall is in said intermediate position and will be polarized in ether of two perpendicularly related planes when said wall is in said first or second position.

7. A universal horn antenna for radio energy of predetermined frequency and of various polarizations comprising substantially rectangularly related pairs of opposed side walls forming a section of open-ended generally rectangular wave guide, the width of one pair of said walls being different from that of the other pair of Walls throughout at least a portion of said section and the length of said section being proportioned to its transverse dimensions so that energy travelling through said section at said frequency and polarized parallel to one of said walls will undergo aphase shift of n times 180 relative to similar energy polarized parallel to the other pair of walls, where :2 equals any integer, whereby when elliptically polarized energy is fed into the input end of said guide the components of the energy polarized parallel to each pair of said rectangularly related walls at the output end will, at any time, bear the same ratio to one another as do the corresponding components of the input energy.

8. An open-ended horn antenna for elliptically polarized radio energy of predetermined frequency comprising an elongated section of generally rectangular wave guide having one pair of its side walls wider than the other, the length of said section being proportioned to the transverse dimensions of said walls that energy travelling through said section at said frequency and polarized parallel to one pair of said walls will undergo a phase shift of n times 180 relative to similar energy polarized parallel to the other pair of walls, where n equals any integer.

9. An open-ended horn antenna for elliptically polan'zed radio energy of predetermined frequency comprising an elongated section of generally rectangular wave guide, at least one pair of its side walls tapering in width between the input and output ends thereof, the shape of the openings defined by the ends of the walls being different at said input and output ends, the length of said section being proportional to its transverse dimensions that energy travelling through said section at said frequency and polarized parallel to one pair of its walls will undergo a phase shift of n times 180 relative to similar energy polarized parallel to the other pair of Walls, where n equals any integer.

10. A polarization switch for radio energy comprising three sections of generally rectangular wave guide connected in end-to-end relationship, the intermediate section being oriented about its axis so that the walls thereof lie in planes forming angles with the walls of the other sections to resolve the energy into two substantially rectangularly related components parallel to said walls, one wall of said intermediate section being movable to vary the cross-sectional shape of said section and thereby the relative phase velocity of those components of said radio energy travelling along said guide and polarized parallel to said movable wall,

11. A polarization switch for radio energy comprising an elongated section of hollow generally rectangular wave guide adapted to transmit radio energy therethrough, means for coupling wave energy into said wave guide at one end with energy polarized at an angle relative to the walls of said guide to resolve the energy into two substantially rectangularly related components parallel to said walls, and means for varying one of the dimensions of said guide so as to vary the relative phase of said components as they emerge at the output end of said guide whereby to vary the polarization of the resultant of said components at said output end.

12. A polarization switch for radio energy comprising an elongated section of hollow generally rectangular wave guide adapted to transmit radio energy therethrough, means for coupling wave energy into said wave guide at one end with radio energy polarized at an acute angle to the walls of said guide to resolve the energy into two substantially rectangularly related components parallel to said walls, said wave guide being constructed to provide for varying one of the internal dimensions thereof so as to correspondingly vary the relative phase of said components as they arrive at the output end of said guide whereby to shift the polarization of the resultant of said energy components at said output end.

13. A polarization switch for radio energy comprising a first section of generally rectangular wave guide adapted to transmit radio waves therethrough polarized parallel to one pair of its walls, a second section of generally rectangular wave guide, a transition section interposed between and coupling said wave guide sections, said second section being oriented about its axis so that its Walls lie in planes at angles to the walls of said first section to resolve the waves into two substantially rectangularly related components polarized parallel to its walls, a pair of opposite walls of said second section extending laterally beyond the juncture of the transition section with said second section, another wall of said second section being mounted for movement within the extended portion of said pair of walls toward and away from its opposite wall to vary the cross sectional shape of said second section and the relative phase velocity of those components of said radio energy travelling along said section and polarized parallel to said movable Wall.

References Cited in the file of this patent UNITED STATES PATENTS 2,602,893 Ratliff July 8, 1952 2,611,087 Alford Sept. 16, 1952 FOREIGN PATENTS 965,881 France Feb. 22, 1950 

